Removal of aromatics, sulphur, or unsaturates from hydrocarbons



Patented Mar. 7, 1944 2,343,841 REMOVAL OF AROMATICS, SULPHUR, R

UNSATURATES.

Robert E. Burk, Clevela to The Standard Oil a corporation of Ohio NoDrawing. Application June 8, 1943. Serial No. 490,078

12 Claims. (Cl. 196-13) Crude petroleum, and the various fractions thatcan be obtained therefrom by distillation, as well as hydrocarbonmixtures and fractions obtained synthetically and by various processingoperations, are comprised of a mixture of a number of difl'erent typesof compounds. Of these types of compounds the saturates comprise a largeportion, particularly the paraiiins. and to a lesser extent thenaphthenes. Many other compounds are included, among them beingaromatics, aliphatic unsaturates, and sulphur compounds.

For many purposes it is undesirable to have all or a plurality of thesediii'erent types of compounds in admixture. For numerous uses it isessential that a fraction or product be free from one or more of severaltypes of these compounds.

For example, it is important in a great many instances (except in thecase of asphalt and tars) that pretroleum and hydrocarbon fractions andproducts be free from sulphur or at least have a stated minimum sulphurcontent. Gasoline should be relatively sulphuz free to make itcompatible with lead. Motor fuel containing sulphur in the form ofmercaptans is undesirable because these sulphur compounds have anunpleasant odor and catalyze gum formation. Sulphur is objectionable infuel oil and kerosene because it burns to form sulphur dioxide which isobnoxious and harmful.

For many other purposes it is desirable that petroleum fractions andproducts be free from aromatics (as well as sulphur in many cases).Lubricating oils, for example, which have only a small amount of certainaromatics have much better viscosity characteristics with reference totemperature, 1.

dom from smoking when used as an illuminant.

Certain unsaturates are undesirable in many petroleum products; thus thepresence of highly unsaturated compounds in lubricating oil results inpolymerization of these unsaturates under the conditions of their use toform gums and other undesirabl products; they are also acted upon byoxygen to form sludge. The presence of highly unsaturated compounds ingasoline is undesirable for the same reason.

The above considerations are directed generally to instances where it isdesirable to remove unwanted compounds such as sulphur, certainaromatics and highly unsaturated material from saturates which comprisethe wanted product. In some cases, however, the compound to e., a higherviscosity index. Kerosene free from aromatics has greater freebe removedmay be the wanted product. In the FROM HYDROCARBONS nd Heights, Ohio,assignor Company, Cleveland, Ohio,

case of aromatics, for example, it is some times desirable to recoverthe aromatics present in fractions of natural petroleum, or those formedby aromatizing, or other processing operations on petroleum hydrocarbonsor distillates from other sources. The aromatics thus separated andrecovered are useful in the production of toluene for nitration, intoluene substitute solvents and other solvents, and in the production ofaromatic naphthas having good blending characteristics useful in themanufacture of aviation fuels. In some instances the aromatics may bethe major constituent of a product, and it may be desirable to treat theproduct to separate minor amounts of other compounds therefrom.

It has been proposed previously to remove sulphur from petroleumproducts and the problem of sulphur removal is as old as the petroleumindustry. The character of the crudes available indicates that it willcontinue to be a problem. Numerous proposals have been made, such as thedoctor solution which converts the ,mercaptan sulphur compounds todisulphides. has the disadvantage that the lead is precipitated as thesulphide and can be regenerated only through time-consuming and hightemperature operations. Treatment with copper chloride solutionsimilarly converts mercaptans to disulphides but is objectionable forthe same reason as the lead treatment and for the additional reason thattraces of copper remain in the hydrocarbon which catalyze gum formation.It has also been proposed to remove sulphur and mercaptans with causticby conversion to disulphides, but this process like the others discussedabove, requires the removal of the disulphides if all sulphur is to beeliminated and also requires large amounts of caustic unless the causticis regenerated. Adsorption with bauxite and similar oxides is anotherproposal but this process, too, uses up the adsorbent unless it isregenerated through high temperature operations involving difllculties.

Dearomatizing has also been proposed by means of solvent extraction butthe solvents available heretofore have also exerted some solvent actionon paraflins and naphthenes, so that the arcmatics could not berecovered in a relatively pure state from saturates.

In accordance with this invention, it has been discovered that sulphur,aromatics or highly unsaturated compounds such as diand polyolefms, orany combination of them, can be removed from petroleum or hydrocarbonscontaining the same by means of a novel solvent-catalyst. The compoundsseparated will depend on the con If the material comprises saturatedhydrocarbons containing aromatics, or sulphur, or highlyimsaturatedcompounds. then treatment in accordance withthe invention will removethese aromatics, sulphur or unsaturates. respectively.Ifthemaierialcontains anytwoofthem,|uchas aromatics and sulphur, bothwill be removed simultaneously, or if the material contains all of them,all three will be removed simultaneously.

y made relatively sulphur free and. therefore. compatible with lead toincrease its octane rating. Fuel oils and .kerosenes may have theiraromatic or sulphur content lowered or removed to improve burningqualities. Lubricating oil may be improved as to its viscosity andanti-sludge forming characteristics. be improved to facilitate theirfurther processing. Diesel fuels may be refined to remove aromatics dthus increase their cetane number as well as r uce their sulphurcontent. Aromatics may be removed from gas oils in order to improve themas cycle stock for cracking. Other fractions may be treated as will beapparent to one skilled in the art. in view of the disclosure being madeherein.

The process is generally applied in the liquid phase, the material beingtreated and the novel solvent-catalyst being thoroughly mixed and thenpermitted to stratify or separated centrifugally. The aromatics, sulphuror unsaturates or. any combination of them, go in the solvent-catalystphase. Two layers areformed, the upper being the. extracted orraffinatephase and the lower layer containing the solventecatalyst andthe separated compounds. The two layers can be readily separated.

The process has the advantage that the solvent-catalyst is relativelylow boiling and can be separated by simple heating to a low temperatureand reused. It is not deleteriously affected and can be recycled andreused indefinitely. This is to be distinguished from prior processes ofremoving sulphur,- as discussed heretoforafor enample, where theremoving agent is used up, or can be regenerated only with hightemperature and otherwise diflicult operations.

The process also has the advantage that the solvent-catalyst used inaccordancewiththe invention does not separate parai'fins or naphthenes.

This'is of particular advantage when theprocess is used fordearomatization, and is to be dismeans of the invention, gasoline maybeI Crudes and reduced crudes may The solvent-catalyst referred tocomprises hydrogen fluoride in the liquid phase and boron trifiuoridedissolved therein (generally with pressure) as the active and essentialingredients. This material seems to form a complex or loose chemicalcombination, with the materials to be removed. or at least some of them.In this respect the material is not a solvent in the sense that organicmaterials are referred to as selective solvents. The material also is acatalyst for some reactions involving hydrocarbons, although under theconditions of use, in accordance with this invention, there are probablyfew reactions in which it exerts a catalytic eifect. same material alsomay be used as a catalyst, it will be referred to herein as a"solvent-catalys for want of a better term.

The solvent-catalyst is used in the liquid phase. The amount, based onthe hydrocarbon fraction or stock to be treated may vary depending onthe amount and nature of the material to be rewill vary somewhat withthe material to be treat-' moved. The amount is not critical except thatenough must be used to permit stratification and separation as twolayers. It is obvious that it is not economical to use more than willbenecessary to accomplish the articular separation desired. In someinstances amounts of the order of 10% are more eilicient than largeramounts of the' orderof 'l00%.- In generahandsubiect to the abovedefinition, the amount will be about Ito 300 volume per cent based onthe stock to be treated. v f

The relative proportions of hydrogen fluoride and boron trifiuoride mayvary from a trace to mol per cent of boron trifiuoride based on theamount of hydrogen fluoride. The composition 1 ed and the product to beremoved. In the retinguished from processes using solvents pro-,

posed heretofore for dearomatizing.

The process of the invention has the additional advantage that itpermits the simultaneous removal. of a plurality .of diflerent types ofcompounds. In many cases it is desirable to remove unsaturates, sulphurand aromatics, or any two of them it contained in the stock tobetreated, and this can be accomplished in accordance with the invention,in a single operation.

In addition, the process has the advantage that the compounds removedwith the solvent-catalyst may be recovered. This is important in thecase of aromatics, particularly where aromatics and sulphur are notseparated simultaneously and where the process is used-for recovering,concentrating or purif aromatics. While the process no doubt could beworked out similarly, with reference to sulphur and unsaturates.possibly in a somewhat changed form. the value of the latter two is notsuch as to warrant the application of the invention to their recovery.

moval of sulphur from heavy stocks, hydrogen fluoride alone may be used,but it alone is not suitable for lighter fractions. The amount of borontrifiuoride can be expressed conveniently in terms of its partialpressure. Since it is a gas (B. P.

- F.) at the temperatures at which the process is carried out, it willbe necessary to have it under pressure during the treatment. The largerthe amount employed the higher will be the partial pressure exerted bythe boron' trifiuoride. In general, partial pressures from 2 to 500pounds per square inch may be used.

The temperature employed is generally from about --30 to 225 F. Thehigher temperatures are sometimes preferable when heavy stocks are to betreated in order to reduce the viscosity. At higher temperatures alsothere may be some cracking or other reactions occasioned by thecatalytic character of the fluorides. The temperature to be used shouldbe selected with this in mind. In general, temperatures from 32 to 150F. are suitable. I Since hydrogen fluoride is relatively low boiling (B.P. 67 F.) it is necessary to use pressure if temperatures above this areused and a closed system is preferred at any event to prevent loss of.the fluoride. In general. a higher pressure is not required than isnecessary to maintain the desired amount of the two fluorides in thetreating zone.

In carrying out the process the hydrocarbon material to be treated andthe solvent-catalyst are mixed thoroughlyby any suitable apparatus. Thereaction occurs rather promptly and the time required may vary from afew minutes to several hours depending on the temperature and otherinterrelated factors. Generally half an hour is Since the I suiiicient,and with temperature of 2 I to contain only 4% eflicient equipment andconditions shorter times are satisfactory. Countercurrent extraction isnot necessary although it may be used. Y

After the reaction is complete or has proceeded to the desired extent,the solvent-catalyst phase is separated from the rafllnate in aconvenient manner, such as by settling, decantation, centrifuging, etc.

If the solvent-catalyst extract is under pressure, the pressure may bereleased and the fluorides will be liberated upon the application ofheat. In general, it is not necessary or desirable to heat the extractbeyond that necessary to release the fluorides, both for reasons ofefiiciency and in order not to modify the extracted materials or tovaporize them if they are low boiling.

Any fluorides that may remain in the railinate can be removed generallyby heating, since the fluorides are volatile at slightly elevatedtemperatures. Alternatively, the phases may be contacted with water.

The anhydrous fluorides recovered from the extract and any from theraflinate may be condensed for reuse. The process is adapted for acontinuous type operation in which the fluorides are continuouslyrecovered and continuously used to treat fresh incoming stoc Thefollowing examples are given as illustrative of the application of theinvention to dearomatizing. In this process the aromatics are thought toform a complex or loose chemical combination with the fluorides which isreadily decomposed or broken down at higher temperatures withoutsubstantial modification of the aromatics, This suggests that lowertemperatures for the treatment may give more complete removal but thereare, no doubt, other factors which influence the equilibrium.

As an illustrative example, a hydrocarbon fraction boiling within therange of 117-380 F. derived from Illinois crude, and containing 10%aromatics, was treated at 32 F. for one hour with 104 volume percenthydrogen fluoride based on the volume of the stock and with borontrifluoride to provide a parti l s u e f 150 pounds per square inch. Themixture was per mitted to stratify and the upper layer was found tocontain 5% aromatics (Kattwinkel). A procedure identical therewith,except that a. tempera ture of 14 F. was used, results in an upper layercontaining 3% aromatics.

A naphtha from Illinois stock containing 13% aromatics was treated forone-half hour at a F. with 50 volume percent hydrogen fluoride based onthe volume of the naphtha charge. The amount of boron tri fluoride usedwas 0.1225 part by weight of the naphtha charge. The mixture waspermitted to stratifyand the top layer. drawn oil. Analysis showed it tocontain 4% aromatics Kattwinkel) In a further illustration ofthe-invention, a kerosene from Illinois stock containing 17%n aromaticswas treated for 0.66 hour with 51 65 volume per cent of hydrogenfluoride based on the kerosene charge and with 01115 part by weightboronfluoride based on the weight of the kerosene charge. The .raflinatecomprises 86.25% by volume ofthe charge and was found aromatics(Kattwinkel) and to have a bromine number of .Oindicating that anyunsaturatesorig'inally present were also removed. The fluorides wereremoved from the extract layer and it was then distilled. The 76 portiondistilling below 410' F. comprises 40% of this fraction. Analysis of thedistillate showed it to contain over aromatics (Kattwinkei). The brominenumber of the distillate was 19.6 indicating that unsaturates had beenremoved from the kerosene by the process.

In the event that a hydrocarbon fraction is to be dearomatized beforeaveraging or other catalytic reactions with hydrogen fluoride andcatalyst, it is possible to use the fluoride catalyst remaining fromsaid catalytic reaction for treatment of further stock to bedearomatized.

As illustrative of the application ofthe invention to the removalvofsulphur, a Mississippi gas oil stock was utilized as the material to betreated. This had a sulphur content of 206%, a bromine number of 4.2(indicating a small amount of unsaturates), and an aromatic content of20%. The gas oil was treated for onehalf hour at 85 to 97 F. with thesolvent-catalyst in an amount of 138% by weight based on the amount ofgas oil. The solvent-catalystused comprised 86.4% hydrogen fluoride and13.6% boron trifluoride. This gave a boron trifluoride partial pressureof 52 pounds per square inch. The total pressure was 60 pounds persquare inch. The railinate was found to contain .063% sulphur indicatinga removal of about 65% of the sulphur. The aromatic content was reducedto 6% and the bromine number to 0.16.

The same gas oil stock was treated with a smaller amount of the samesolvent-catalyst and at a lower temperature, i. e., the amount used was71% by weight of the stock and the temperature was 78 to 85 F. The totalpressure was 30 pounds per square inch. The raflinate comprises 80.2% ofthe charge and contained .09% sulphur. The extract, after removal of thesolvent-catalyst, contained 1.045% sulphur.

As further illustrative of the application of the invention to theremoval of sulphur, a reduced Yazoo crude oil was treated in accordancewith the invention. This reduced crude had an initial sulphur content of0.85% and a viscosity gravity constant of 0.836. The reduced crude wastreated for fifteen minutes at a temperature of F. with 10 volume percent hydrogen fluoride based on the amount of reduced crude, and 4.3weight per cent boron trifluoride based on the reduced crude. At the'endof this treatment the rafinate was found to comprise 77% of the reducedcrude charge and to have a sulphur content of 0.17%. The viscositygravity constant of the raflinate was found to be 0.816.

The invention is applicable to the treatment of lubricating oils toimprove their viscosity index (through removal of aromatics) and todecrease their tendency to form carbon, and sludge, as well as theremoval of sulphur present in the oil. The mode of application of theinventionto lubricating oils will be readily apparent.

The invention is also applicableto the treatment of crude oil. Theremoval of sulphur'from crude will be reflected in'all later processingoperations. -The sulphur removal may be accompanied by catalytiecracking, averaging, and other reactions which the solvent-catalystcatalyzes, but these are'of minor significance unless appropriateconditions. are selected to favor them. v

It is recognized that Hofmann et al. have proposed the treatment oflubricating oil with a small amount of hydrogen fluoride.

it is subjected to boron trifluoride as the In their- 4 process thefluorides apparently were used to catalyze the polymerization ofunsaturates. The

too small to as the flueoff without constituents amount used also wasapparently permit stratiflcation or extraction, rides in their processwere distilled any attempt at separation of any with the; fluorides in,the liquid phase.

leave the impurities behind. The manner in which the inventiondistinguishes from the process is readily apparent.- I

' This application is a continuation-in-part of application Serial No.423,303, flled December 1'1, 1941. V

The invention is subject to many modifications and variations as will beapparent from this description and I intend all of the same tobeincluded within the invention as one within the scope of the followingclaims:

I claim:

1. A process of treating hydrocarbons to separate any compound of anunsaturated, aromatic or sulphurous nature that may be present therein,which comprises admixing said hydrocarbons containing at least one ofsaid compounds with liquid hydrogen fluoride containing a minorproportion of boron trifluoride under a pressure to maintain thehydrogen fluoride liquid under conditions' such that the primary, actionis the formation of a fluoride complex with any of said compounds, andseparating the mixture into two layers, the heavier layer containingsaid fluoride complex.

2. A process of treating hydrocarbons to separate any compound of anunsaturated, aromatic or sulphurous nature that may be present therein,which comprises admixing said hydrocarbons containing at least one ofsaid compounds with to 300 volume percent liquid hydrogen fluoride andan amount of boron trifluoride to provide a partial pressure of 2 to,500 pounds per square inch at a temperature of -30 to 225 F., and undera pressure to maintain the hydrogen fluoride liquid, the conditionswithin the above recited ranges being selected such that the primaryaction is the formation of a fluoride complex with-any of saidcompounds, whereupon the mixture may be separated into lighter andheavier layers with said fluoride complex in the heavier layer; andseparating the layers.

3. A process of treating hydrocarbons to separate any compound of anunsaturated, aromatic or sulphurous nature that may be present therein,which comprises admixing said hydrocarbons containing at least one ofsaid compounds with 5 to 150 volume percent liquid hydrogen fluoride andan amountof boron trifluoride to provide a partial pressure of 25-to 200pounds per square inch, at a temperature of 32 to 110 F., and under apressure to maintain the hydrogen fluoride liquid, the conditions withinthe above recited ranges being selected such that the primary action isthe formation of may be separated into lighter and heavier layers thelatter containing said fluoride complex; removing the lighter layer;removing the heavier layer and heating it to release the fluoridescontained therein.

4. A process for separating any compounds of an unsaturated, aromatic orsulphurous nature that may be contained in petroleum and petroleumfractions; which comprises subjecting the Follow-. ing. this thelubricating oil was distilled off to a fluoride complex with 'any ofsaid compounds, whereupon the mixtur 55 containing a minor proportion ofboron trifluoride under conditions such that the primary action is theformation of a fluoride complex with any of said compounds; andseparating the resulting mixture into two layers, the heavier comprisingthe fluorides and said fluoride complex.

5. A process for separating any compounds of an .unsaturated, aromaticor sulphurous nature that may be contained in petroleum and petroleumfractions; which comprises subjecting the same to the action of 5 to 300volume percent liquid hydrogen fluoride and an amount of borontrifluoride to provide a partial pressure of 2 to 500 pounds per squareinch, at a temperature of 30 to 225 F., and at a pressure to maintainthe hydrogen fluoride liquid, the conditions within the above recitedranges being selected such that the primary action is the formation of afluoride complex with any of said compounds, separating the resultingmixture into two layers, the heavier comprising the fluorides and saidfluoride complex; separating the two layers; and heating the heavierlayer to recover the fluorides therefrom.

6. A process for separating any compounds of an unsaturated, aromatic orsulphurous nature that may be contained in petroleum and petroleumfractions; which comprises subjecting the same to the action of 5 to 150volume percent liquid hydrogen fluoride and an amount of borontrifluoride to provide a partial pressure of 25 to 200 pounds per squareinch, at a temperature of 32 to F., and at a pressure to maintain thehydrogen fluoride liquid, the conditions within the above recited rangesbeing selected such that the primary action is the formation of afluoride complex with any of said compounds, separating the resultingmixture into two layers, the heavier comprising the fluorides and saidfluoride complex; and separating the two layers.

7. A process for separating any compounds of an unsaturated, aromatic orsulphurous nature that may be contained in crude oil; which comprisessubjecting the crude to the action of liquid hydrogen fluoride and aminor proportion of boron trifluoride under conditions such that theprimary action is the formation of a fluoride complex with any of saidcompounds; separating the resulting mixture into two layers, the heaviercomprising the fluorides and said fluoride complex and separating thetwo layers.

8. A process for separating any compounds of an unsaturated, aromatic orsulphurous nature that may be contained in a petroleum distillatefraction; which comprises subjecting the same to the action of liquidhydrogen fluoride and a minor proportion of boron trifluoride underconditions such that the primary action is the formation of a fluoridecomplex with any of said compounds; separating the resulting mixtureinto two layers, the heavier comprising the fluorides and said fluoridecomplex; and separating the two layers.

9. A process of treating lubricating oil stock to separate therefromcompounds of an unsaturated, aromatic or sulphurous nature that may becontained therein; which comprises subjecting the same to theaction ofliquid hydrogen fluoride and a minor proportion of boron trifluorideunder conditions such that th primary action is the formation of afluoride complex with any of said compounds separating the resultingmixture into two layers, the heavier comprising the fluorides and saidfluoride complex; and separating same to the action of liquid hydrogenfluoride 15 the two layers.

10. A process of treating lubricating oil stock to separate therefromcompounds of an unsaturated, aromatic or sulphurous nature that may becontained therein; which comprises subjecting the same to the action ofto 200 volume percent liquid hydrogen fluoride and an amount of borontrifluoride to provide a partial pressure of 2 to 500 pounds per squareinch, at a temperature of -30 to 225 F., and at a pressure to maintainthe hydrogen fluoride liquid; the conditions within the above recitedranges being selected such that the primary action is the formation of afluoride complex with any of said compounds, separating the resultingmixture into two layers, the heavier comprising the fluorides and saidfluoride complex and the lower layer comprising the treated lubricatedoil stock; separating the two layers; and recovering the fluorides fromthe heavier layer.

11. A process of desulphurizing hydrocarbons; which comprises subjectinga sulphur containing hydrocarbon to the action of liquid hydrogenfluoiide and a minor proportion of boron trifluoride under conditionssuch that the primary action is the separation and transfer of thesulphur compounds from the hydrocarbons to the fluorides; forming theresulting mixture into two layers, the heavier comprising the fluoridesand sulphur compounds separated from the hydrocarbons; and separatingthe two layers.

12. A process of desulphurizing petroleum and petroleum fractionscontaining sulphurous compounds; which comprises mixing the same with 5to 300 volume percent liquid hydrogen fluoride and an amount of borontrifluoride to provide a partial pressure of 2 to 500 pounds per squareinch, at a temperature of to 225 F., and at a pressure to maintain thehydrogen fluoride liquid, the conditions within the above recited rangesbeing selected such that the primary action is the transfer ofsulphurous compounds from the petroleum and the petroleum fractions tothe liquid fluoride; forming the resulting mixture into two layers, theheavier comprising the fluorides and sulphur compounds separated fromthe petroleum and petroleum fractions; separating the two layers; andrecovering the fluorides from the heavier layer.

ROBERT E. BURK.

